Quaternary isothermal vapor-liquid equilibrium of the model biofuel 2-butanone + n-heptane + tetrahydrofuran + cyclohexane using Raman spectroscopic characterization

Abstract

Vapor-liquid equilibrium data of fuel mixtures are of major importance for both fuel production as well as combustion. However, the measurement of vapor-liquid equilibrium data usually requires significant experimental effort. The experimental effort is particularly high if multicomponent mixtures are of interest, as experimental effort rises strongly with a rising number of components. In this work, we efficiently characterize the vapor-liquid equilibrium of a quaternary model biofuel and its binary subsystems. For this purpose, we employ the recently developed milliliter-scale Raman Spectroscopic Phase Equilibrium Characterization (RAMSPEQU)-setup. Vapor pressures are collected at T = 283–333 K, and isothermal pTx-data for mixtures at T = 303.2 K resulting in a pressure range of p = 2.8–81.9 kPa. The PCP-SAFT equation of state is used for thermodynamic modeling. Our binary data agrees well with experimental data from literature. The quaternary phase behavior is predicted with very good accuracy using PCP-SAFT with parameters adjusted to pure substance and binary mixture data only. The milliliter-scale setup allows us to characterize the phase equilibria with just 22 ml (binary) and less than 105 ml (quaternary) of the respective mixtures. The agreement of predicted and experimental quaternary phase equilibrium data indicate the reliability of the employed method for multicomponent vapor-liquid equilibrium measurements.